blob: 2d013f01ce2c9a433eb721b6890642ecd32af5c9 [file] [log] [blame]
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include <limits.h>
#include <signal.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include "config.h"
#ifdef HAVE_DL_ITERATE_PHDR
#include <link.h>
#endif
#include "runtime.h"
#include "arch.h"
#include "defs.h"
#include "malloc.h"
#include "go-type.h"
#include "go-defer.h"
#ifdef USING_SPLIT_STACK
/* FIXME: These are not declared anywhere. */
extern void __splitstack_getcontext(void *context[10]);
extern void __splitstack_setcontext(void *context[10]);
extern void *__splitstack_makecontext(size_t, void *context[10], size_t *);
extern void * __splitstack_resetcontext(void *context[10], size_t *);
extern void *__splitstack_find(void *, void *, size_t *, void **, void **,
void **);
extern void __splitstack_block_signals (int *, int *);
extern void __splitstack_block_signals_context (void *context[10], int *,
int *);
#endif
#ifndef PTHREAD_STACK_MIN
# define PTHREAD_STACK_MIN 8192
#endif
#if defined(USING_SPLIT_STACK) && defined(LINKER_SUPPORTS_SPLIT_STACK)
# define StackMin PTHREAD_STACK_MIN
#else
# define StackMin ((sizeof(char *) < 8) ? 2 * 1024 * 1024 : 4 * 1024 * 1024)
#endif
uintptr runtime_stacks_sys;
static void gtraceback(G*);
#ifdef __rtems__
#define __thread
#endif
static __thread G *g;
static __thread M *m;
#ifndef SETCONTEXT_CLOBBERS_TLS
static inline void
initcontext(void)
{
}
static inline void
fixcontext(ucontext_t *c __attribute__ ((unused)))
{
}
#else
# if defined(__x86_64__) && defined(__sun__)
// x86_64 Solaris 10 and 11 have a bug: setcontext switches the %fs
// register to that of the thread which called getcontext. The effect
// is that the address of all __thread variables changes. This bug
// also affects pthread_self() and pthread_getspecific. We work
// around it by clobbering the context field directly to keep %fs the
// same.
static __thread greg_t fs;
static inline void
initcontext(void)
{
ucontext_t c;
getcontext(&c);
fs = c.uc_mcontext.gregs[REG_FSBASE];
}
static inline void
fixcontext(ucontext_t* c)
{
c->uc_mcontext.gregs[REG_FSBASE] = fs;
}
# elif defined(__NetBSD__)
// NetBSD has a bug: setcontext clobbers tlsbase, we need to save
// and restore it ourselves.
static __thread __greg_t tlsbase;
static inline void
initcontext(void)
{
ucontext_t c;
getcontext(&c);
tlsbase = c.uc_mcontext._mc_tlsbase;
}
static inline void
fixcontext(ucontext_t* c)
{
c->uc_mcontext._mc_tlsbase = tlsbase;
}
# elif defined(__sparc__)
static inline void
initcontext(void)
{
}
static inline void
fixcontext(ucontext_t *c)
{
/* ??? Using
register unsigned long thread __asm__("%g7");
c->uc_mcontext.gregs[REG_G7] = thread;
results in
error: variable ‘thread’ might be clobbered by \
‘longjmp’ or ‘vfork’ [-Werror=clobbered]
which ought to be false, as %g7 is a fixed register. */
if (sizeof (c->uc_mcontext.gregs[REG_G7]) == 8)
asm ("stx %%g7, %0" : "=m"(c->uc_mcontext.gregs[REG_G7]));
else
asm ("st %%g7, %0" : "=m"(c->uc_mcontext.gregs[REG_G7]));
}
# else
# error unknown case for SETCONTEXT_CLOBBERS_TLS
# endif
#endif
// We can not always refer to the TLS variables directly. The
// compiler will call tls_get_addr to get the address of the variable,
// and it may hold it in a register across a call to schedule. When
// we get back from the call we may be running in a different thread,
// in which case the register now points to the TLS variable for a
// different thread. We use non-inlinable functions to avoid this
// when necessary.
G* runtime_g(void) __attribute__ ((noinline, no_split_stack));
G*
runtime_g(void)
{
return g;
}
M* runtime_m(void) __attribute__ ((noinline, no_split_stack));
M*
runtime_m(void)
{
return m;
}
// Set m and g.
void
runtime_setmg(M* mp, G* gp)
{
m = mp;
g = gp;
}
// Start a new thread.
static void
runtime_newosproc(M *mp)
{
pthread_attr_t attr;
sigset_t clear, old;
pthread_t tid;
int ret;
if(pthread_attr_init(&attr) != 0)
runtime_throw("pthread_attr_init");
if(pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) != 0)
runtime_throw("pthread_attr_setdetachstate");
// Block signals during pthread_create so that the new thread
// starts with signals disabled. It will enable them in minit.
sigfillset(&clear);
#ifdef SIGTRAP
// Blocking SIGTRAP reportedly breaks gdb on Alpha GNU/Linux.
sigdelset(&clear, SIGTRAP);
#endif
sigemptyset(&old);
pthread_sigmask(SIG_BLOCK, &clear, &old);
ret = pthread_create(&tid, &attr, runtime_mstart, mp);
pthread_sigmask(SIG_SETMASK, &old, nil);
if (ret != 0)
runtime_throw("pthread_create");
}
// First function run by a new goroutine. This replaces gogocall.
static void
kickoff(void)
{
void (*fn)(void*);
if(g->traceback != nil)
gtraceback(g);
fn = (void (*)(void*))(g->entry);
fn(g->param);
runtime_goexit();
}
// Switch context to a different goroutine. This is like longjmp.
void runtime_gogo(G*) __attribute__ ((noinline));
void
runtime_gogo(G* newg)
{
#ifdef USING_SPLIT_STACK
__splitstack_setcontext(&newg->stack_context[0]);
#endif
g = newg;
newg->fromgogo = true;
fixcontext(&newg->context);
setcontext(&newg->context);
runtime_throw("gogo setcontext returned");
}
// Save context and call fn passing g as a parameter. This is like
// setjmp. Because getcontext always returns 0, unlike setjmp, we use
// g->fromgogo as a code. It will be true if we got here via
// setcontext. g == nil the first time this is called in a new m.
void runtime_mcall(void (*)(G*)) __attribute__ ((noinline));
void
runtime_mcall(void (*pfn)(G*))
{
M *mp;
G *gp;
// Ensure that all registers are on the stack for the garbage
// collector.
__builtin_unwind_init();
mp = m;
gp = g;
if(gp == mp->g0)
runtime_throw("runtime: mcall called on m->g0 stack");
if(gp != nil) {
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&g->stack_context[0]);
#else
gp->gcnext_sp = &pfn;
#endif
gp->fromgogo = false;
getcontext(&gp->context);
// When we return from getcontext, we may be running
// in a new thread. That means that m and g may have
// changed. They are global variables so we will
// reload them, but the addresses of m and g may be
// cached in our local stack frame, and those
// addresses may be wrong. Call functions to reload
// the values for this thread.
mp = runtime_m();
gp = runtime_g();
if(gp->traceback != nil)
gtraceback(gp);
}
if (gp == nil || !gp->fromgogo) {
#ifdef USING_SPLIT_STACK
__splitstack_setcontext(&mp->g0->stack_context[0]);
#endif
mp->g0->entry = (byte*)pfn;
mp->g0->param = gp;
// It's OK to set g directly here because this case
// can not occur if we got here via a setcontext to
// the getcontext call just above.
g = mp->g0;
fixcontext(&mp->g0->context);
setcontext(&mp->g0->context);
runtime_throw("runtime: mcall function returned");
}
}
// Goroutine scheduler
// The scheduler's job is to distribute ready-to-run goroutines over worker threads.
//
// The main concepts are:
// G - goroutine.
// M - worker thread, or machine.
// P - processor, a resource that is required to execute Go code.
// M must have an associated P to execute Go code, however it can be
// blocked or in a syscall w/o an associated P.
//
// Design doc at http://golang.org/s/go11sched.
typedef struct Sched Sched;
struct Sched {
Lock lock;
uint64 goidgen;
M* midle; // idle m's waiting for work
int32 nmidle; // number of idle m's waiting for work
int32 nmidlelocked; // number of locked m's waiting for work
int32 mcount; // number of m's that have been created
int32 maxmcount; // maximum number of m's allowed (or die)
P* pidle; // idle P's
uint32 npidle;
uint32 nmspinning;
// Global runnable queue.
G* runqhead;
G* runqtail;
int32 runqsize;
// Global cache of dead G's.
Lock gflock;
G* gfree;
uint32 gcwaiting; // gc is waiting to run
int32 stopwait;
Note stopnote;
uint32 sysmonwait;
Note sysmonnote;
uint64 lastpoll;
int32 profilehz; // cpu profiling rate
};
enum
{
// The max value of GOMAXPROCS.
// There are no fundamental restrictions on the value.
MaxGomaxprocs = 1<<8,
// Number of goroutine ids to grab from runtime_sched.goidgen to local per-P cache at once.
// 16 seems to provide enough amortization, but other than that it's mostly arbitrary number.
GoidCacheBatch = 16,
};
Sched runtime_sched;
int32 runtime_gomaxprocs;
uint32 runtime_needextram = 1;
M runtime_m0;
G runtime_g0; // idle goroutine for m0
G* runtime_lastg;
M* runtime_allm;
P** runtime_allp;
M* runtime_extram;
int8* runtime_goos;
int32 runtime_ncpu;
bool runtime_precisestack;
static int32 newprocs;
static Lock allglock; // the following vars are protected by this lock or by stoptheworld
G** runtime_allg;
uintptr runtime_allglen;
static uintptr allgcap;
bool runtime_isarchive;
void* runtime_mstart(void*);
static void runqput(P*, G*);
static G* runqget(P*);
static bool runqputslow(P*, G*, uint32, uint32);
static G* runqsteal(P*, P*);
static void mput(M*);
static M* mget(void);
static void mcommoninit(M*);
static void schedule(void);
static void procresize(int32);
static void acquirep(P*);
static P* releasep(void);
static void newm(void(*)(void), P*);
static void stopm(void);
static void startm(P*, bool);
static void handoffp(P*);
static void wakep(void);
static void stoplockedm(void);
static void startlockedm(G*);
static void sysmon(void);
static uint32 retake(int64);
static void incidlelocked(int32);
static void checkdead(void);
static void exitsyscall0(G*);
static void park0(G*);
static void goexit0(G*);
static void gfput(P*, G*);
static G* gfget(P*);
static void gfpurge(P*);
static void globrunqput(G*);
static void globrunqputbatch(G*, G*, int32);
static G* globrunqget(P*, int32);
static P* pidleget(void);
static void pidleput(P*);
static void injectglist(G*);
static bool preemptall(void);
static bool exitsyscallfast(void);
static void allgadd(G*);
bool runtime_isstarted;
// The bootstrap sequence is:
//
// call osinit
// call schedinit
// make & queue new G
// call runtime_mstart
//
// The new G calls runtime_main.
void
runtime_schedinit(void)
{
int32 n, procs;
String s;
const byte *p;
Eface i;
m = &runtime_m0;
g = &runtime_g0;
m->g0 = g;
m->curg = g;
g->m = m;
initcontext();
runtime_sched.maxmcount = 10000;
runtime_precisestack = 0;
// runtime_symtabinit();
runtime_mallocinit();
mcommoninit(m);
// Initialize the itable value for newErrorCString,
// so that the next time it gets called, possibly
// in a fault during a garbage collection, it will not
// need to allocated memory.
runtime_newErrorCString(0, &i);
// Initialize the cached gotraceback value, since
// gotraceback calls getenv, which mallocs on Plan 9.
runtime_gotraceback(nil);
runtime_goargs();
runtime_goenvs();
runtime_parsedebugvars();
runtime_sched.lastpoll = runtime_nanotime();
procs = 1;
s = runtime_getenv("GOMAXPROCS");
p = s.str;
if(p != nil && (n = runtime_atoi(p, s.len)) > 0) {
if(n > MaxGomaxprocs)
n = MaxGomaxprocs;
procs = n;
}
runtime_allp = runtime_malloc((MaxGomaxprocs+1)*sizeof(runtime_allp[0]));
procresize(procs);
// Can not enable GC until all roots are registered.
// mstats.enablegc = 1;
}
extern void main_init(void) __asm__ (GOSYM_PREFIX "__go_init_main");
extern void main_main(void) __asm__ (GOSYM_PREFIX "main.main");
// Used to determine the field alignment.
struct field_align
{
char c;
Hchan *p;
};
// main_init_done is a signal used by cgocallbackg that initialization
// has been completed. It is made before _cgo_notify_runtime_init_done,
// so all cgo calls can rely on it existing. When main_init is
// complete, it is closed, meaning cgocallbackg can reliably receive
// from it.
Hchan *runtime_main_init_done;
// The chan bool type, for runtime_main_init_done.
extern const struct __go_type_descriptor bool_type_descriptor
__asm__ (GOSYM_PREFIX "__go_tdn_bool");
static struct __go_channel_type chan_bool_type_descriptor =
{
/* __common */
{
/* __code */
GO_CHAN,
/* __align */
__alignof (Hchan *),
/* __field_align */
offsetof (struct field_align, p) - 1,
/* __size */
sizeof (Hchan *),
/* __hash */
0, /* This value doesn't matter. */
/* __hashfn */
&__go_type_hash_error_descriptor,
/* __equalfn */
&__go_type_equal_error_descriptor,
/* __gc */
NULL, /* This value doesn't matter */
/* __reflection */
NULL, /* This value doesn't matter */
/* __uncommon */
NULL,
/* __pointer_to_this */
NULL
},
/* __element_type */
&bool_type_descriptor,
/* __dir */
CHANNEL_BOTH_DIR
};
extern Hchan *__go_new_channel (ChanType *, uintptr);
extern void closechan(Hchan *) __asm__ (GOSYM_PREFIX "runtime.closechan");
static void
initDone(void *arg __attribute__ ((unused))) {
runtime_unlockOSThread();
};
// The main goroutine.
// Note: C frames in general are not copyable during stack growth, for two reasons:
// 1) We don't know where in a frame to find pointers to other stack locations.
// 2) There's no guarantee that globals or heap values do not point into the frame.
//
// The C frame for runtime.main is copyable, because:
// 1) There are no pointers to other stack locations in the frame
// (d.fn points at a global, d.link is nil, d.argp is -1).
// 2) The only pointer into this frame is from the defer chain,
// which is explicitly handled during stack copying.
void
runtime_main(void* dummy __attribute__((unused)))
{
Defer d;
_Bool frame;
newm(sysmon, nil);
// Lock the main goroutine onto this, the main OS thread,
// during initialization. Most programs won't care, but a few
// do require certain calls to be made by the main thread.
// Those can arrange for main.main to run in the main thread
// by calling runtime.LockOSThread during initialization
// to preserve the lock.
runtime_lockOSThread();
// Defer unlock so that runtime.Goexit during init does the unlock too.
d.__pfn = initDone;
d.__next = g->defer;
d.__arg = (void*)-1;
d.__panic = g->panic;
d.__retaddr = nil;
d.__makefunc_can_recover = 0;
d.__frame = &frame;
d.__special = true;
g->defer = &d;
if(m != &runtime_m0)
runtime_throw("runtime_main not on m0");
__go_go(runtime_MHeap_Scavenger, nil);
runtime_main_init_done = __go_new_channel(&chan_bool_type_descriptor, 0);
_cgo_notify_runtime_init_done();
main_init();
closechan(runtime_main_init_done);
if(g->defer != &d || d.__pfn != initDone)
runtime_throw("runtime: bad defer entry after init");
g->defer = d.__next;
runtime_unlockOSThread();
// For gccgo we have to wait until after main is initialized
// to enable GC, because initializing main registers the GC
// roots.
mstats.enablegc = 1;
if(runtime_isarchive) {
// This is not a complete program, but is instead a
// library built using -buildmode=c-archive or
// c-shared. Now that we are initialized, there is
// nothing further to do.
return;
}
main_main();
// Make racy client program work: if panicking on
// another goroutine at the same time as main returns,
// let the other goroutine finish printing the panic trace.
// Once it does, it will exit. See issue 3934.
if(runtime_panicking)
runtime_park(nil, nil, "panicwait");
runtime_exit(0);
for(;;)
*(int32*)0 = 0;
}
void
runtime_goroutineheader(G *gp)
{
const char *status;
int64 waitfor;
switch(gp->status) {
case Gidle:
status = "idle";
break;
case Grunnable:
status = "runnable";
break;
case Grunning:
status = "running";
break;
case Gsyscall:
status = "syscall";
break;
case Gwaiting:
if(gp->waitreason)
status = gp->waitreason;
else
status = "waiting";
break;
default:
status = "???";
break;
}
// approx time the G is blocked, in minutes
waitfor = 0;
if((gp->status == Gwaiting || gp->status == Gsyscall) && gp->waitsince != 0)
waitfor = (runtime_nanotime() - gp->waitsince) / (60LL*1000*1000*1000);
if(waitfor < 1)
runtime_printf("goroutine %D [%s]:\n", gp->goid, status);
else
runtime_printf("goroutine %D [%s, %D minutes]:\n", gp->goid, status, waitfor);
}
void
runtime_printcreatedby(G *g)
{
if(g != nil && g->gopc != 0 && g->goid != 1) {
String fn;
String file;
intgo line;
if(__go_file_line(g->gopc - 1, &fn, &file, &line)) {
runtime_printf("created by %S\n", fn);
runtime_printf("\t%S:%D\n", file, (int64) line);
}
}
}
struct Traceback
{
G* gp;
Location locbuf[TracebackMaxFrames];
int32 c;
};
void
runtime_tracebackothers(G * volatile me)
{
G * volatile gp;
Traceback tb;
int32 traceback;
volatile uintptr i;
tb.gp = me;
traceback = runtime_gotraceback(nil);
// Show the current goroutine first, if we haven't already.
if((gp = m->curg) != nil && gp != me) {
runtime_printf("\n");
runtime_goroutineheader(gp);
gp->traceback = &tb;
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&me->stack_context[0]);
#endif
getcontext(&me->context);
if(gp->traceback != nil) {
runtime_gogo(gp);
}
runtime_printtrace(tb.locbuf, tb.c, false);
runtime_printcreatedby(gp);
}
runtime_lock(&allglock);
for(i = 0; i < runtime_allglen; i++) {
gp = runtime_allg[i];
if(gp == me || gp == m->curg || gp->status == Gdead)
continue;
if(gp->issystem && traceback < 2)
continue;
runtime_printf("\n");
runtime_goroutineheader(gp);
// Our only mechanism for doing a stack trace is
// _Unwind_Backtrace. And that only works for the
// current thread, not for other random goroutines.
// So we need to switch context to the goroutine, get
// the backtrace, and then switch back.
// This means that if g is running or in a syscall, we
// can't reliably print a stack trace. FIXME.
if(gp->status == Grunning) {
runtime_printf("\tgoroutine running on other thread; stack unavailable\n");
runtime_printcreatedby(gp);
} else if(gp->status == Gsyscall) {
runtime_printf("\tgoroutine in C code; stack unavailable\n");
runtime_printcreatedby(gp);
} else {
gp->traceback = &tb;
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&me->stack_context[0]);
#endif
getcontext(&me->context);
if(gp->traceback != nil) {
runtime_gogo(gp);
}
runtime_printtrace(tb.locbuf, tb.c, false);
runtime_printcreatedby(gp);
}
}
runtime_unlock(&allglock);
}
static void
checkmcount(void)
{
// sched lock is held
if(runtime_sched.mcount > runtime_sched.maxmcount) {
runtime_printf("runtime: program exceeds %d-thread limit\n", runtime_sched.maxmcount);
runtime_throw("thread exhaustion");
}
}
// Do a stack trace of gp, and then restore the context to
// gp->dotraceback.
static void
gtraceback(G* gp)
{
Traceback* traceback;
traceback = gp->traceback;
gp->traceback = nil;
traceback->c = runtime_callers(1, traceback->locbuf,
sizeof traceback->locbuf / sizeof traceback->locbuf[0], false);
runtime_gogo(traceback->gp);
}
static void
mcommoninit(M *mp)
{
// If there is no mcache runtime_callers() will crash,
// and we are most likely in sysmon thread so the stack is senseless anyway.
if(m->mcache)
runtime_callers(1, mp->createstack, nelem(mp->createstack), false);
mp->fastrand = 0x49f6428aUL + mp->id + runtime_cputicks();
runtime_lock(&runtime_sched.lock);
mp->id = runtime_sched.mcount++;
checkmcount();
runtime_mpreinit(mp);
// Add to runtime_allm so garbage collector doesn't free m
// when it is just in a register or thread-local storage.
mp->alllink = runtime_allm;
// runtime_NumCgoCall() iterates over allm w/o schedlock,
// so we need to publish it safely.
runtime_atomicstorep(&runtime_allm, mp);
runtime_unlock(&runtime_sched.lock);
}
// Mark gp ready to run.
void
runtime_ready(G *gp)
{
// Mark runnable.
m->locks++; // disable preemption because it can be holding p in a local var
if(gp->status != Gwaiting) {
runtime_printf("goroutine %D has status %d\n", gp->goid, gp->status);
runtime_throw("bad g->status in ready");
}
gp->status = Grunnable;
runqput(m->p, gp);
if(runtime_atomicload(&runtime_sched.npidle) != 0 && runtime_atomicload(&runtime_sched.nmspinning) == 0) // TODO: fast atomic
wakep();
m->locks--;
}
int32
runtime_gcprocs(void)
{
int32 n;
// Figure out how many CPUs to use during GC.
// Limited by gomaxprocs, number of actual CPUs, and MaxGcproc.
runtime_lock(&runtime_sched.lock);
n = runtime_gomaxprocs;
if(n > runtime_ncpu)
n = runtime_ncpu > 0 ? runtime_ncpu : 1;
if(n > MaxGcproc)
n = MaxGcproc;
if(n > runtime_sched.nmidle+1) // one M is currently running
n = runtime_sched.nmidle+1;
runtime_unlock(&runtime_sched.lock);
return n;
}
static bool
needaddgcproc(void)
{
int32 n;
runtime_lock(&runtime_sched.lock);
n = runtime_gomaxprocs;
if(n > runtime_ncpu)
n = runtime_ncpu;
if(n > MaxGcproc)
n = MaxGcproc;
n -= runtime_sched.nmidle+1; // one M is currently running
runtime_unlock(&runtime_sched.lock);
return n > 0;
}
void
runtime_helpgc(int32 nproc)
{
M *mp;
int32 n, pos;
runtime_lock(&runtime_sched.lock);
pos = 0;
for(n = 1; n < nproc; n++) { // one M is currently running
if(runtime_allp[pos]->mcache == m->mcache)
pos++;
mp = mget();
if(mp == nil)
runtime_throw("runtime_gcprocs inconsistency");
mp->helpgc = n;
mp->mcache = runtime_allp[pos]->mcache;
pos++;
runtime_notewakeup(&mp->park);
}
runtime_unlock(&runtime_sched.lock);
}
// Similar to stoptheworld but best-effort and can be called several times.
// There is no reverse operation, used during crashing.
// This function must not lock any mutexes.
void
runtime_freezetheworld(void)
{
int32 i;
if(runtime_gomaxprocs == 1)
return;
// stopwait and preemption requests can be lost
// due to races with concurrently executing threads,
// so try several times
for(i = 0; i < 5; i++) {
// this should tell the scheduler to not start any new goroutines
runtime_sched.stopwait = 0x7fffffff;
runtime_atomicstore((uint32*)&runtime_sched.gcwaiting, 1);
// this should stop running goroutines
if(!preemptall())
break; // no running goroutines
runtime_usleep(1000);
}
// to be sure
runtime_usleep(1000);
preemptall();
runtime_usleep(1000);
}
void
runtime_stoptheworld(void)
{
int32 i;
uint32 s;
P *p;
bool wait;
runtime_lock(&runtime_sched.lock);
runtime_sched.stopwait = runtime_gomaxprocs;
runtime_atomicstore((uint32*)&runtime_sched.gcwaiting, 1);
preemptall();
// stop current P
m->p->status = Pgcstop;
runtime_sched.stopwait--;
// try to retake all P's in Psyscall status
for(i = 0; i < runtime_gomaxprocs; i++) {
p = runtime_allp[i];
s = p->status;
if(s == Psyscall && runtime_cas(&p->status, s, Pgcstop))
runtime_sched.stopwait--;
}
// stop idle P's
while((p = pidleget()) != nil) {
p->status = Pgcstop;
runtime_sched.stopwait--;
}
wait = runtime_sched.stopwait > 0;
runtime_unlock(&runtime_sched.lock);
// wait for remaining P's to stop voluntarily
if(wait) {
runtime_notesleep(&runtime_sched.stopnote);
runtime_noteclear(&runtime_sched.stopnote);
}
if(runtime_sched.stopwait)
runtime_throw("stoptheworld: not stopped");
for(i = 0; i < runtime_gomaxprocs; i++) {
p = runtime_allp[i];
if(p->status != Pgcstop)
runtime_throw("stoptheworld: not stopped");
}
}
static void
mhelpgc(void)
{
m->helpgc = -1;
}
void
runtime_starttheworld(void)
{
P *p, *p1;
M *mp;
G *gp;
bool add;
m->locks++; // disable preemption because it can be holding p in a local var
gp = runtime_netpoll(false); // non-blocking
injectglist(gp);
add = needaddgcproc();
runtime_lock(&runtime_sched.lock);
if(newprocs) {
procresize(newprocs);
newprocs = 0;
} else
procresize(runtime_gomaxprocs);
runtime_sched.gcwaiting = 0;
p1 = nil;
while((p = pidleget()) != nil) {
// procresize() puts p's with work at the beginning of the list.
// Once we reach a p without a run queue, the rest don't have one either.
if(p->runqhead == p->runqtail) {
pidleput(p);
break;
}
p->m = mget();
p->link = p1;
p1 = p;
}
if(runtime_sched.sysmonwait) {
runtime_sched.sysmonwait = false;
runtime_notewakeup(&runtime_sched.sysmonnote);
}
runtime_unlock(&runtime_sched.lock);
while(p1) {
p = p1;
p1 = p1->link;
if(p->m) {
mp = p->m;
p->m = nil;
if(mp->nextp)
runtime_throw("starttheworld: inconsistent mp->nextp");
mp->nextp = p;
runtime_notewakeup(&mp->park);
} else {
// Start M to run P. Do not start another M below.
newm(nil, p);
add = false;
}
}
if(add) {
// If GC could have used another helper proc, start one now,
// in the hope that it will be available next time.
// It would have been even better to start it before the collection,
// but doing so requires allocating memory, so it's tricky to
// coordinate. This lazy approach works out in practice:
// we don't mind if the first couple gc rounds don't have quite
// the maximum number of procs.
newm(mhelpgc, nil);
}
m->locks--;
}
// Called to start an M.
void*
runtime_mstart(void* mp)
{
m = (M*)mp;
g = m->g0;
initcontext();
g->entry = nil;
g->param = nil;
// Record top of stack for use by mcall.
// Once we call schedule we're never coming back,
// so other calls can reuse this stack space.
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&g->stack_context[0]);
#else
g->gcinitial_sp = &mp;
// Setting gcstack_size to 0 is a marker meaning that gcinitial_sp
// is the top of the stack, not the bottom.
g->gcstack_size = 0;
g->gcnext_sp = &mp;
#endif
getcontext(&g->context);
if(g->entry != nil) {
// Got here from mcall.
void (*pfn)(G*) = (void (*)(G*))g->entry;
G* gp = (G*)g->param;
pfn(gp);
*(int*)0x21 = 0x21;
}
runtime_minit();
#ifdef USING_SPLIT_STACK
{
int dont_block_signals = 0;
__splitstack_block_signals(&dont_block_signals, nil);
}
#endif
// Install signal handlers; after minit so that minit can
// prepare the thread to be able to handle the signals.
if(m == &runtime_m0) {
if(runtime_iscgo && !runtime_cgoHasExtraM) {
runtime_cgoHasExtraM = true;
runtime_newextram();
runtime_needextram = 0;
}
runtime_initsig();
}
if(m->mstartfn)
m->mstartfn();
if(m->helpgc) {
m->helpgc = 0;
stopm();
} else if(m != &runtime_m0) {
acquirep(m->nextp);
m->nextp = nil;
}
schedule();
// TODO(brainman): This point is never reached, because scheduler
// does not release os threads at the moment. But once this path
// is enabled, we must remove our seh here.
return nil;
}
typedef struct CgoThreadStart CgoThreadStart;
struct CgoThreadStart
{
M *m;
G *g;
uintptr *tls;
void (*fn)(void);
};
// Allocate a new m unassociated with any thread.
// Can use p for allocation context if needed.
M*
runtime_allocm(P *p, int32 stacksize, byte** ret_g0_stack, size_t* ret_g0_stacksize)
{
M *mp;
m->locks++; // disable GC because it can be called from sysmon
if(m->p == nil)
acquirep(p); // temporarily borrow p for mallocs in this function
#if 0
if(mtype == nil) {
Eface e;
runtime_gc_m_ptr(&e);
mtype = ((const PtrType*)e.__type_descriptor)->__element_type;
}
#endif
mp = runtime_mal(sizeof *mp);
mcommoninit(mp);
mp->g0 = runtime_malg(stacksize, ret_g0_stack, ret_g0_stacksize);
if(p == m->p)
releasep();
m->locks--;
return mp;
}
static G*
allocg(void)
{
G *gp;
// static Type *gtype;
// if(gtype == nil) {
// Eface e;
// runtime_gc_g_ptr(&e);
// gtype = ((PtrType*)e.__type_descriptor)->__element_type;
// }
// gp = runtime_cnew(gtype);
gp = runtime_malloc(sizeof(G));
return gp;
}
static M* lockextra(bool nilokay);
static void unlockextra(M*);
// needm is called when a cgo callback happens on a
// thread without an m (a thread not created by Go).
// In this case, needm is expected to find an m to use
// and return with m, g initialized correctly.
// Since m and g are not set now (likely nil, but see below)
// needm is limited in what routines it can call. In particular
// it can only call nosplit functions (textflag 7) and cannot
// do any scheduling that requires an m.
//
// In order to avoid needing heavy lifting here, we adopt
// the following strategy: there is a stack of available m's
// that can be stolen. Using compare-and-swap
// to pop from the stack has ABA races, so we simulate
// a lock by doing an exchange (via casp) to steal the stack
// head and replace the top pointer with MLOCKED (1).
// This serves as a simple spin lock that we can use even
// without an m. The thread that locks the stack in this way
// unlocks the stack by storing a valid stack head pointer.
//
// In order to make sure that there is always an m structure
// available to be stolen, we maintain the invariant that there
// is always one more than needed. At the beginning of the
// program (if cgo is in use) the list is seeded with a single m.
// If needm finds that it has taken the last m off the list, its job
// is - once it has installed its own m so that it can do things like
// allocate memory - to create a spare m and put it on the list.
//
// Each of these extra m's also has a g0 and a curg that are
// pressed into service as the scheduling stack and current
// goroutine for the duration of the cgo callback.
//
// When the callback is done with the m, it calls dropm to
// put the m back on the list.
//
// Unlike the gc toolchain, we start running on curg, since we are
// just going to return and let the caller continue.
void
runtime_needm(void)
{
M *mp;
if(runtime_needextram) {
// Can happen if C/C++ code calls Go from a global ctor.
// Can not throw, because scheduler is not initialized yet.
int rv __attribute__((unused));
rv = runtime_write(2, "fatal error: cgo callback before cgo call\n",
sizeof("fatal error: cgo callback before cgo call\n")-1);
runtime_exit(1);
}
// Lock extra list, take head, unlock popped list.
// nilokay=false is safe here because of the invariant above,
// that the extra list always contains or will soon contain
// at least one m.
mp = lockextra(false);
// Set needextram when we've just emptied the list,
// so that the eventual call into cgocallbackg will
// allocate a new m for the extra list. We delay the
// allocation until then so that it can be done
// after exitsyscall makes sure it is okay to be
// running at all (that is, there's no garbage collection
// running right now).
mp->needextram = mp->schedlink == nil;
unlockextra(mp->schedlink);
// Install m and g (= m->curg).
runtime_setmg(mp, mp->curg);
// Initialize g's context as in mstart.
initcontext();
g->status = Gsyscall;
g->entry = nil;
g->param = nil;
#ifdef USING_SPLIT_STACK
__splitstack_getcontext(&g->stack_context[0]);
#else
g->gcinitial_sp = &mp;
g->gcstack = nil;
g->gcstack_size = 0;
g->gcnext_sp = &mp;
#endif
getcontext(&g->context);
if(g->entry != nil) {
// Got here from mcall.
void (*pfn)(G*) = (void (*)(G*))g->entry;
G* gp = (G*)g->param;
pfn(gp);
*(int*)0x22 = 0x22;
}
// Initialize this thread to use the m.
runtime_minit();
#ifdef USING_SPLIT_STACK
{
int dont_block_signals = 0;
__splitstack_block_signals(&dont_block_signals, nil);
}
#endif
}
// newextram allocates an m and puts it on the extra list.
// It is called with a working local m, so that it can do things
// like call schedlock and allocate.
void
runtime_newextram(void)
{
M *mp, *mnext;
G *gp;
byte *g0_sp, *sp;
size_t g0_spsize, spsize;
// Create extra goroutine locked to extra m.
// The goroutine is the context in which the cgo callback will run.
// The sched.pc will never be returned to, but setting it to
// runtime.goexit makes clear to the traceback routines where
// the goroutine stack ends.
mp = runtime_allocm(nil, StackMin, &g0_sp, &g0_spsize);
gp = runtime_malg(StackMin, &sp, &spsize);
gp->status = Gdead;
mp->curg = gp;
mp->locked = LockInternal;
mp->lockedg = gp;
gp->lockedm = mp;
gp->goid = runtime_xadd64(&runtime_sched.goidgen, 1);
// put on allg for garbage collector
allgadd(gp);
// The context for gp will be set up in runtime_needm. But
// here we need to set up the context for g0.
getcontext(&mp->g0->context);
mp->g0->context.uc_stack.ss_sp = g0_sp;
mp->g0->context.uc_stack.ss_size = g0_spsize;
makecontext(&mp->g0->context, kickoff, 0);
// Add m to the extra list.
mnext = lockextra(true);
mp->schedlink = mnext;
unlockextra(mp);
}
// dropm is called when a cgo callback has called needm but is now
// done with the callback and returning back into the non-Go thread.
// It puts the current m back onto the extra list.
//
// The main expense here is the call to signalstack to release the
// m's signal stack, and then the call to needm on the next callback
// from this thread. It is tempting to try to save the m for next time,
// which would eliminate both these costs, but there might not be
// a next time: the current thread (which Go does not control) might exit.
// If we saved the m for that thread, there would be an m leak each time
// such a thread exited. Instead, we acquire and release an m on each
// call. These should typically not be scheduling operations, just a few
// atomics, so the cost should be small.
//
// TODO(rsc): An alternative would be to allocate a dummy pthread per-thread
// variable using pthread_key_create. Unlike the pthread keys we already use
// on OS X, this dummy key would never be read by Go code. It would exist
// only so that we could register at thread-exit-time destructor.
// That destructor would put the m back onto the extra list.
// This is purely a performance optimization. The current version,
// in which dropm happens on each cgo call, is still correct too.
// We may have to keep the current version on systems with cgo
// but without pthreads, like Windows.
void
runtime_dropm(void)
{
M *mp, *mnext;
// Undo whatever initialization minit did during needm.
runtime_unminit();
// Clear m and g, and return m to the extra list.
// After the call to setmg we can only call nosplit functions.
mp = m;
runtime_setmg(nil, nil);
mp->curg->status = Gdead;
mp->curg->gcstack = nil;
mp->curg->gcnext_sp = nil;
mnext = lockextra(true);
mp->schedlink = mnext;
unlockextra(mp);
}
#define MLOCKED ((M*)1)
// lockextra locks the extra list and returns the list head.
// The caller must unlock the list by storing a new list head
// to runtime.extram. If nilokay is true, then lockextra will
// return a nil list head if that's what it finds. If nilokay is false,
// lockextra will keep waiting until the list head is no longer nil.
static M*
lockextra(bool nilokay)
{
M *mp;
void (*yield)(void);
for(;;) {
mp = runtime_atomicloadp(&runtime_extram);
if(mp == MLOCKED) {
yield = runtime_osyield;
yield();
continue;
}
if(mp == nil && !nilokay) {
runtime_usleep(1);
continue;
}
if(!runtime_casp(&runtime_extram, mp, MLOCKED)) {
yield = runtime_osyield;
yield();
continue;
}
break;
}
return mp;
}
static void
unlockextra(M *mp)
{
runtime_atomicstorep(&runtime_extram, mp);
}
static int32
countextra()
{
M *mp, *mc;
int32 c;
for(;;) {
mp = runtime_atomicloadp(&runtime_extram);
if(mp == MLOCKED) {
runtime_osyield();
continue;
}
if(!runtime_casp(&runtime_extram, mp, MLOCKED)) {
runtime_osyield();
continue;
}
c = 0;
for(mc = mp; mc != nil; mc = mc->schedlink)
c++;
runtime_atomicstorep(&runtime_extram, mp);
return c;
}
}
// Create a new m. It will start off with a call to fn, or else the scheduler.
static void
newm(void(*fn)(void), P *p)
{
M *mp;
mp = runtime_allocm(p, -1, nil, nil);
mp->nextp = p;
mp->mstartfn = fn;
runtime_newosproc(mp);
}
// Stops execution of the current m until new work is available.
// Returns with acquired P.
static void
stopm(void)
{
if(m->locks)
runtime_throw("stopm holding locks");
if(m->p)
runtime_throw("stopm holding p");
if(m->spinning) {
m->spinning = false;
runtime_xadd(&runtime_sched.nmspinning, -1);
}
retry:
runtime_lock(&runtime_sched.lock);
mput(m);
runtime_unlock(&runtime_sched.lock);
runtime_notesleep(&m->park);
runtime_noteclear(&m->park);
if(m->helpgc) {
runtime_gchelper();
m->helpgc = 0;
m->mcache = nil;
goto retry;
}
acquirep(m->nextp);
m->nextp = nil;
}
static void
mspinning(void)
{
m->spinning = true;
}
// Schedules some M to run the p (creates an M if necessary).
// If p==nil, tries to get an idle P, if no idle P's does nothing.
static void
startm(P *p, bool spinning)
{
M *mp;
void (*fn)(void);
runtime_lock(&runtime_sched.lock);
if(p == nil) {
p = pidleget();
if(p == nil) {
runtime_unlock(&runtime_sched.lock);
if(spinning)
runtime_xadd(&runtime_sched.nmspinning, -1);
return;
}
}
mp = mget();
runtime_unlock(&runtime_sched.lock);
if(mp == nil) {
fn = nil;
if(spinning)
fn = mspinning;
newm(fn, p);
return;
}
if(mp->spinning)
runtime_throw("startm: m is spinning");
if(mp->nextp)
runtime_throw("startm: m has p");
mp->spinning = spinning;
mp->nextp = p;
runtime_notewakeup(&mp->park);
}
// Hands off P from syscall or locked M.
static void
handoffp(P *p)
{
// if it has local work, start it straight away
if(p->runqhead != p->runqtail || runtime_sched.runqsize) {
startm(p, false);
return;
}
// no local work, check that there are no spinning/idle M's,
// otherwise our help is not required
if(runtime_atomicload(&runtime_sched.nmspinning) + runtime_atomicload(&runtime_sched.npidle) == 0 && // TODO: fast atomic
runtime_cas(&runtime_sched.nmspinning, 0, 1)) {
startm(p, true);
return;
}
runtime_lock(&runtime_sched.lock);
if(runtime_sched.gcwaiting) {
p->status = Pgcstop;
if(--runtime_sched.stopwait == 0)
runtime_notewakeup(&runtime_sched.stopnote);
runtime_unlock(&runtime_sched.lock);
return;
}
if(runtime_sched.runqsize) {
runtime_unlock(&runtime_sched.lock);
startm(p, false);
return;
}
// If this is the last running P and nobody is polling network,
// need to wakeup another M to poll network.
if(runtime_sched.npidle == (uint32)runtime_gomaxprocs-1 && runtime_atomicload64(&runtime_sched.lastpoll) != 0) {
runtime_unlock(&runtime_sched.lock);
startm(p, false);
return;
}
pidleput(p);
runtime_unlock(&runtime_sched.lock);
}
// Tries to add one more P to execute G's.
// Called when a G is made runnable (newproc, ready).
static void
wakep(void)
{
// be conservative about spinning threads
if(!runtime_cas(&runtime_sched.nmspinning, 0, 1))
return;
startm(nil, true);
}
// Stops execution of the current m that is locked to a g until the g is runnable again.
// Returns with acquired P.
static void
stoplockedm(void)
{
P *p;
if(m->lockedg == nil || m->lockedg->lockedm != m)
runtime_throw("stoplockedm: inconsistent locking");
if(m->p) {
// Schedule another M to run this p.
p = releasep();
handoffp(p);
}
incidlelocked(1);
// Wait until another thread schedules lockedg again.
runtime_notesleep(&m->park);
runtime_noteclear(&m->park);
if(m->lockedg->status != Grunnable)
runtime_throw("stoplockedm: not runnable");
acquirep(m->nextp);
m->nextp = nil;
}
// Schedules the locked m to run the locked gp.
static void
startlockedm(G *gp)
{
M *mp;
P *p;
mp = gp->lockedm;
if(mp == m)
runtime_throw("startlockedm: locked to me");
if(mp->nextp)
runtime_throw("startlockedm: m has p");
// directly handoff current P to the locked m
incidlelocked(-1);
p = releasep();
mp->nextp = p;
runtime_notewakeup(&mp->park);
stopm();
}
// Stops the current m for stoptheworld.
// Returns when the world is restarted.
static void
gcstopm(void)
{
P *p;
if(!runtime_sched.gcwaiting)
runtime_throw("gcstopm: not waiting for gc");
if(m->spinning) {
m->spinning = false;
runtime_xadd(&runtime_sched.nmspinning, -1);
}
p = releasep();
runtime_lock(&runtime_sched.lock);
p->status = Pgcstop;
if(--runtime_sched.stopwait == 0)
runtime_notewakeup(&runtime_sched.stopnote);
runtime_unlock(&runtime_sched.lock);
stopm();
}
// Schedules gp to run on the current M.
// Never returns.
static void
execute(G *gp)
{
int32 hz;
if(gp->status != Grunnable) {
runtime_printf("execute: bad g status %d\n", gp->status);
runtime_throw("execute: bad g status");
}
gp->status = Grunning;
gp->waitsince = 0;
m->p->schedtick++;
m->curg = gp;
gp->m = m;
// Check whether the profiler needs to be turned on or off.
hz = runtime_sched.profilehz;
if(m->profilehz != hz)
runtime_resetcpuprofiler(hz);
runtime_gogo(gp);
}
// Finds a runnable goroutine to execute.
// Tries to steal from other P's, get g from global queue, poll network.
static G*
findrunnable(void)
{
G *gp;
P *p;
int32 i;
top:
if(runtime_sched.gcwaiting) {
gcstopm();
goto top;
}
if(runtime_fingwait && runtime_fingwake && (gp = runtime_wakefing()) != nil)
runtime_ready(gp);
// local runq
gp = runqget(m->p);
if(gp)
return gp;
// global runq
if(runtime_sched.runqsize) {
runtime_lock(&runtime_sched.lock);
gp = globrunqget(m->p, 0);
runtime_unlock(&runtime_sched.lock);
if(gp)
return gp;
}
// poll network
gp = runtime_netpoll(false); // non-blocking
if(gp) {
injectglist(gp->schedlink);
gp->status = Grunnable;
return gp;
}
// If number of spinning M's >= number of busy P's, block.
// This is necessary to prevent excessive CPU consumption
// when GOMAXPROCS>>1 but the program parallelism is low.
if(!m->spinning && 2 * runtime_atomicload(&runtime_sched.nmspinning) >= runtime_gomaxprocs - runtime_atomicload(&runtime_sched.npidle)) // TODO: fast atomic
goto stop;
if(!m->spinning) {
m->spinning = true;
runtime_xadd(&runtime_sched.nmspinning, 1);
}
// random steal from other P's
for(i = 0; i < 2*runtime_gomaxprocs; i++) {
if(runtime_sched.gcwaiting)
goto top;
p = runtime_allp[runtime_fastrand1()%runtime_gomaxprocs];
if(p == m->p)
gp = runqget(p);
else
gp = runqsteal(m->p, p);
if(gp)
return gp;
}
stop:
// return P and block
runtime_lock(&runtime_sched.lock);
if(runtime_sched.gcwaiting) {
runtime_unlock(&runtime_sched.lock);
goto top;
}
if(runtime_sched.runqsize) {
gp = globrunqget(m->p, 0);
runtime_unlock(&runtime_sched.lock);
return gp;
}
p = releasep();
pidleput(p);
runtime_unlock(&runtime_sched.lock);
if(m->spinning) {
m->spinning = false;
runtime_xadd(&runtime_sched.nmspinning, -1);
}
// check all runqueues once again
for(i = 0; i < runtime_gomaxprocs; i++) {
p = runtime_allp[i];
if(p && p->runqhead != p->runqtail) {
runtime_lock(&runtime_sched.lock);
p = pidleget();
runtime_unlock(&runtime_sched.lock);
if(p) {
acquirep(p);
goto top;
}
break;
}
}
// poll network
if(runtime_xchg64(&runtime_sched.lastpoll, 0) != 0) {
if(m->p)
runtime_throw("findrunnable: netpoll with p");
if(m->spinning)
runtime_throw("findrunnable: netpoll with spinning");
gp = runtime_netpoll(true); // block until new work is available
runtime_atomicstore64(&runtime_sched.lastpoll, runtime_nanotime());
if(gp) {
runtime_lock(&runtime_sched.lock);
p = pidleget();
runtime_unlock(&runtime_sched.lock);
if(p) {
acquirep(p);
injectglist(gp->schedlink);
gp->status = Grunnable;
return gp;
}
injectglist(gp);
}
}
stopm();
goto top;
}
static void
resetspinning(void)
{
int32 nmspinning;
if(m->spinning) {
m->spinning = false;
nmspinning = runtime_xadd(&runtime_sched.nmspinning, -1);
if(nmspinning < 0)
runtime_throw("findrunnable: negative nmspinning");
} else
nmspinning = runtime_atomicload(&runtime_sched.nmspinning);
// M wakeup policy is deliberately somewhat conservative (see nmspinning handling),
// so see if we need to wakeup another P here.
if (nmspinning == 0 && runtime_atomicload(&runtime_sched.npidle) > 0)
wakep();
}
// Injects the list of runnable G's into the scheduler.
// Can run concurrently with GC.
static void
injectglist(G *glist)
{
int32 n;
G *gp;
if(glist == nil)
return;
runtime_lock(&runtime_sched.lock);
for(n = 0; glist; n++) {
gp = glist;
glist = gp->schedlink;
gp->status = Grunnable;
globrunqput(gp);
}
runtime_unlock(&runtime_sched.lock);
for(; n && runtime_sched.npidle; n--)
startm(nil, false);
}
// One round of scheduler: find a runnable goroutine and execute it.
// Never returns.
static void
schedule(void)
{
G *gp;
uint32 tick;
if(m->locks)
runtime_throw("schedule: holding locks");
top:
if(runtime_sched.gcwaiting) {
gcstopm();
goto top;
}
gp = nil;
// Check the global runnable queue once in a while to ensure fairness.
// Otherwise two goroutines can completely occupy the local runqueue
// by constantly respawning each other.
tick = m->p->schedtick;
// This is a fancy way to say tick%61==0,
// it uses 2 MUL instructions instead of a single DIV and so is faster on modern processors.
if(tick - (((uint64)tick*0x4325c53fu)>>36)*61 == 0 && runtime_sched.runqsize > 0) {
runtime_lock(&runtime_sched.lock);
gp = globrunqget(m->p, 1);
runtime_unlock(&runtime_sched.lock);
if(gp)
resetspinning();
}
if(gp == nil) {
gp = runqget(m->p);
if(gp && m->spinning)
runtime_throw("schedule: spinning with local work");
}
if(gp == nil) {
gp = findrunnable(); // blocks until work is available
resetspinning();
}
if(gp->lockedm) {
// Hands off own p to the locked m,
// then blocks waiting for a new p.
startlockedm(gp);
goto top;
}
execute(gp);
}
// Puts the current goroutine into a waiting state and calls unlockf.
// If unlockf returns false, the goroutine is resumed.
void
runtime_park(bool(*unlockf)(G*, void*), void *lock, const char *reason)
{
if(g->status != Grunning)
runtime_throw("bad g status");
m->waitlock = lock;
m->waitunlockf = unlockf;
g->waitreason = reason;
runtime_mcall(park0);
}
static bool
parkunlock(G *gp, void *lock)
{
USED(gp);
runtime_unlock(lock);
return true;
}
// Puts the current goroutine into a waiting state and unlocks the lock.
// The goroutine can be made runnable again by calling runtime_ready(gp).
void
runtime_parkunlock(Lock *lock, const char *reason)
{
runtime_park(parkunlock, lock, reason);
}
// runtime_park continuation on g0.
static void
park0(G *gp)
{
bool ok;
gp->status = Gwaiting;
gp->m = nil;
m->curg = nil;
if(m->waitunlockf) {
ok = m->waitunlockf(gp, m->waitlock);
m->waitunlockf = nil;
m->waitlock = nil;
if(!ok) {
gp->status = Grunnable;
execute(gp); // Schedule it back, never returns.
}
}
if(m->lockedg) {
stoplockedm();
execute(gp); // Never returns.
}
schedule();
}
// Scheduler yield.
void
runtime_gosched(void)
{
if(g->status != Grunning)
runtime_throw("bad g status");
runtime_mcall(runtime_gosched0);
}
// runtime_gosched continuation on g0.
void
runtime_gosched0(G *gp)
{
gp->status = Grunnable;
gp->m = nil;
m->curg = nil;
runtime_lock(&runtime_sched.lock);
globrunqput(gp);
runtime_unlock(&runtime_sched.lock);
if(m->lockedg) {
stoplockedm();
execute(gp); // Never returns.
}
schedule();
}
// Finishes execution of the current goroutine.
// Need to mark it as nosplit, because it runs with sp > stackbase (as runtime_lessstack).
// Since it does not return it does not matter. But if it is preempted
// at the split stack check, GC will complain about inconsistent sp.
void runtime_goexit(void) __attribute__ ((noinline));
void
runtime_goexit(void)
{
if(g->status != Grunning)
runtime_throw("bad g status");
runtime_mcall(goexit0);
}
// runtime_goexit continuation on g0.
static void
goexit0(G *gp)
{
gp->status = Gdead;
gp->entry = nil;
gp->m = nil;
gp->lockedm = nil;
gp->paniconfault = 0;
gp->defer = nil; // should be true already but just in case.
gp->panic = nil; // non-nil for Goexit during panic. points at stack-allocated data.
gp->writenbuf = 0;
gp->writebuf = nil;
gp->waitreason = nil;
gp->param = nil;
m->curg = nil;
m->lockedg = nil;
if(m->locked & ~LockExternal) {
runtime_printf("invalid m->locked = %d\n", m->locked);
runtime_throw("internal lockOSThread error");
}
m->locked = 0;
gfput(m->p, gp);
schedule();
}
// The goroutine g is about to enter a system call.
// Record that it's not using the cpu anymore.
// This is called only from the go syscall library and cgocall,
// not from the low-level system calls used by the runtime.
//
// Entersyscall cannot split the stack: the runtime_gosave must
// make g->sched refer to the caller's stack segment, because
// entersyscall is going to return immediately after.
void runtime_entersyscall(void) __attribute__ ((no_split_stack));
static void doentersyscall(void) __attribute__ ((no_split_stack, noinline));
void
runtime_entersyscall()
{
// Save the registers in the g structure so that any pointers
// held in registers will be seen by the garbage collector.
getcontext(&g->gcregs);
// Do the work in a separate function, so that this function
// doesn't save any registers on its own stack. If this
// function does save any registers, we might store the wrong
// value in the call to getcontext.
//
// FIXME: This assumes that we do not need to save any
// callee-saved registers to access the TLS variable g. We
// don't want to put the ucontext_t on the stack because it is
// large and we can not split the stack here.
doentersyscall();
}
static void
doentersyscall()
{
// Disable preemption because during this function g is in Gsyscall status,
// but can have inconsistent g->sched, do not let GC observe it.
m->locks++;
// Leave SP around for GC and traceback.
#ifdef USING_SPLIT_STACK
g->gcstack = __splitstack_find(nil, nil, &g->gcstack_size,
&g->gcnext_segment, &g->gcnext_sp,
&g->gcinitial_sp);
#else
{
void *v;
g->gcnext_sp = (byte *) &v;
}
#endif
g->status = Gsyscall;
if(runtime_atomicload(&runtime_sched.sysmonwait)) { // TODO: fast atomic
runtime_lock(&runtime_sched.lock);
if(runtime_atomicload(&runtime_sched.sysmonwait)) {
runtime_atomicstore(&runtime_sched.sysmonwait, 0);
runtime_notewakeup(&runtime_sched.sysmonnote);
}
runtime_unlock(&runtime_sched.lock);
}
m->mcache = nil;
m->p->m = nil;
runtime_atomicstore(&m->p->status, Psyscall);
if(runtime_sched.gcwaiting) {
runtime_lock(&runtime_sched.lock);
if (runtime_sched.stopwait > 0 && runtime_cas(&m->p->status, Psyscall, Pgcstop)) {
if(--runtime_sched.stopwait == 0)
runtime_notewakeup(&runtime_sched.stopnote);
}
runtime_unlock(&runtime_sched.lock);
}
m->locks--;
}
// The same as runtime_entersyscall(), but with a hint that the syscall is blocking.
void
runtime_entersyscallblock(void)
{
P *p;
m->locks++; // see comment in entersyscall
// Leave SP around for GC and traceback.
#ifdef USING_SPLIT_STACK
g->gcstack = __splitstack_find(nil, nil, &g->gcstack_size,
&g->gcnext_segment, &g->gcnext_sp,
&g->gcinitial_sp);
#else
g->gcnext_sp = (byte *) &p;
#endif
// Save the registers in the g structure so that any pointers
// held in registers will be seen by the garbage collector.
getcontext(&g->gcregs);
g->status = Gsyscall;
p = releasep();
handoffp(p);
if(g->isbackground) // do not consider blocked scavenger for deadlock detection
incidlelocked(1);
m->locks--;
}
// The goroutine g exited its system call.
// Arrange for it to run on a cpu again.
// This is called only from the go syscall library, not
// from the low-level system calls used by the runtime.
void
runtime_exitsyscall(void)
{
G *gp;
m->locks++; // see comment in entersyscall
gp = g;
if(gp->isbackground) // do not consider blocked scavenger for deadlock detection
incidlelocked(-1);
g->waitsince = 0;
if(exitsyscallfast()) {
// There's a cpu for us, so we can run.
m->p->syscalltick++;
gp->status = Grunning;
// Garbage collector isn't running (since we are),
// so okay to clear gcstack and gcsp.
#ifdef USING_SPLIT_STACK
gp->gcstack = nil;
#endif
gp->gcnext_sp = nil;
runtime_memclr(&gp->gcregs, sizeof gp->gcregs);
m->locks--;
return;
}
m->locks--;
// Call the scheduler.
runtime_mcall(exitsyscall0);
// Scheduler returned, so we're allowed to run now.
// Delete the gcstack information that we left for
// the garbage collector during the system call.
// Must wait until now because until gosched returns
// we don't know for sure that the garbage collector
// is not running.
#ifdef USING_SPLIT_STACK
gp->gcstack = nil;
#endif
gp->gcnext_sp = nil;
runtime_memclr(&gp->gcregs, sizeof gp->gcregs);
// Don't refer to m again, we might be running on a different
// thread after returning from runtime_mcall.
runtime_m()->p->syscalltick++;
}
static bool
exitsyscallfast(void)
{
P *p;
// Freezetheworld sets stopwait but does not retake P's.
if(runtime_sched.stopwait) {
m->p = nil;
return false;
}
// Try to re-acquire the last P.
if(m->p && m->p->status == Psyscall && runtime_cas(&m->p->status, Psyscall, Prunning)) {
// There's a cpu for us, so we can run.
m->mcache = m->p->mcache;
m->p->m = m;
return true;
}
// Try to get any other idle P.
m->p = nil;
if(runtime_sched.pidle) {
runtime_lock(&runtime_sched.lock);
p = pidleget();
if(p && runtime_atomicload(&runtime_sched.sysmonwait)) {
runtime_atomicstore(&runtime_sched.sysmonwait, 0);
runtime_notewakeup(&runtime_sched.sysmonnote);
}
runtime_unlock(&runtime_sched.lock);
if(p) {
acquirep(p);
return true;
}
}
return false;
}
// runtime_exitsyscall slow path on g0.
// Failed to acquire P, enqueue gp as runnable.
static void
exitsyscall0(G *gp)
{
P *p;
gp->status = Grunnable;
gp->m = nil;
m->curg = nil;
runtime_lock(&runtime_sched.lock);
p = pidleget();
if(p == nil)
globrunqput(gp);
else if(runtime_atomicload(&runtime_sched.sysmonwait)) {
runtime_atomicstore(&runtime_sched.sysmonwait, 0);
runtime_notewakeup(&runtime_sched.sysmonnote);
}
runtime_unlock(&runtime_sched.lock);
if(p) {
acquirep(p);
execute(gp); // Never returns.
}
if(m->lockedg) {
// Wait until another thread schedules gp and so m again.
stoplockedm();
execute(gp); // Never returns.
}
stopm();
schedule(); // Never returns.
}
// Called from syscall package before fork.
void syscall_runtime_BeforeFork(void)
__asm__(GOSYM_PREFIX "syscall.runtime_BeforeFork");
void
syscall_runtime_BeforeFork(void)
{
// Fork can hang if preempted with signals frequently enough (see issue 5517).
// Ensure that we stay on the same M where we disable profiling.
runtime_m()->locks++;
if(runtime_m()->profilehz != 0)
runtime_resetcpuprofiler(0);
}
// Called from syscall package after fork in parent.
void syscall_runtime_AfterFork(void)
__asm__(GOSYM_PREFIX "syscall.runtime_AfterFork");
void
syscall_runtime_AfterFork(void)
{
int32 hz;
hz = runtime_sched.profilehz;
if(hz != 0)
runtime_resetcpuprofiler(hz);
runtime_m()->locks--;
}
// Allocate a new g, with a stack big enough for stacksize bytes.
G*
runtime_malg(int32 stacksize, byte** ret_stack, size_t* ret_stacksize)
{
G *newg;
newg = allocg();
if(stacksize >= 0) {
#if USING_SPLIT_STACK
int dont_block_signals = 0;
*ret_stack = __splitstack_makecontext(stacksize,
&newg->stack_context[0],
ret_stacksize);
__splitstack_block_signals_context(&newg->stack_context[0],
&dont_block_signals, nil);
#else
// In 64-bit mode, the maximum Go allocation space is
// 128G. Our stack size is 4M, which only permits 32K
// goroutines. In order to not limit ourselves,
// allocate the stacks out of separate memory. In
// 32-bit mode, the Go allocation space is all of
// memory anyhow.
if(sizeof(void*) == 8) {
void *p = runtime_SysAlloc(stacksize, &mstats.other_sys);
if(p == nil)
runtime_throw("runtime: cannot allocate memory for goroutine stack");
*ret_stack = (byte*)p;
} else {
*ret_stack = runtime_mallocgc(stacksize, 0, FlagNoProfiling|FlagNoGC);
runtime_xadd(&runtime_stacks_sys, stacksize);
}
*ret_stacksize = stacksize;
newg->gcinitial_sp = *ret_stack;
newg->gcstack_size = stacksize;
#endif
}
return newg;
}
/* For runtime package testing. */
// Create a new g running fn with siz bytes of arguments.
// Put it on the queue of g's waiting to run.
// The compiler turns a go statement into a call to this.
// Cannot split the stack because it assumes that the arguments
// are available sequentially after &fn; they would not be
// copied if a stack split occurred. It's OK for this to call
// functions that split the stack.
void runtime_testing_entersyscall(int32)
__asm__ (GOSYM_PREFIX "runtime.entersyscall");
void
runtime_testing_entersyscall(int32 dummy __attribute__ ((unused)))
{
runtime_entersyscall();
}
void runtime_testing_exitsyscall(int32)
__asm__ (GOSYM_PREFIX "runtime.exitsyscall");
void
runtime_testing_exitsyscall(int32 dummy __attribute__ ((unused)))
{
runtime_exitsyscall();
}
G*
__go_go(void (*fn)(void*), void* arg)
{
byte *sp;
size_t spsize;
G *newg;
P *p;
//runtime_printf("newproc1 %p %p narg=%d nret=%d\n", fn->fn, argp, narg, nret);
if(fn == nil) {
m->throwing = -1; // do not dump full stacks
runtime_throw("go of nil func value");
}
m->locks++; // disable preemption because it can be holding p in a local var
p = m->p;
if((newg = gfget(p)) != nil) {
#ifdef USING_SPLIT_STACK
int dont_block_signals = 0;
sp = __splitstack_resetcontext(&newg->stack_context[0],
&spsize);
__splitstack_block_signals_context(&newg->stack_context[0],
&dont_block_signals, nil);
#else
sp = newg->gcinitial_sp;
spsize = newg->gcstack_size;
if(spsize == 0)
runtime_throw("bad spsize in __go_go");
newg->gcnext_sp = sp;
#endif
} else {
newg = runtime_malg(StackMin, &sp, &spsize);
allgadd(newg);
}
newg->entry = (byte*)fn;
newg->param = arg;
newg->gopc = (uintptr)__builtin_return_address(0);
newg->status = Grunnable;
if(p->goidcache == p->goidcacheend) {
p->goidcache = runtime_xadd64(&runtime_sched.goidgen, GoidCacheBatch);
p->goidcacheend = p->goidcache + GoidCacheBatch;
}
newg->goid = p->goidcache++;
{
// Avoid warnings about variables clobbered by
// longjmp.
byte * volatile vsp = sp;
size_t volatile vspsize = spsize;
G * volatile vnewg = newg;
getcontext(&vnewg->context);
vnewg->context.uc_stack.ss_sp = vsp;
#ifdef MAKECONTEXT_STACK_TOP
vnewg->context.uc_stack.ss_sp += vspsize;
#endif
vnewg->context.uc_stack.ss_size = vspsize;
makecontext(&vnewg->context, kickoff, 0);
runqput(p, vnewg);
if(runtime_atomicload(&runtime_sched.npidle) != 0 && runtime_atomicload(&runtime_sched.nmspinning) == 0 && fn != runtime_main) // TODO: fast atomic
wakep();
m->locks--;
return vnewg;
}
}
static void
allgadd(G *gp)
{
G **new;
uintptr cap;
runtime_lock(&allglock);
if(runtime_allglen >= allgcap) {
cap = 4096/sizeof(new[0]);
if(cap < 2*allgcap)
cap = 2*allgcap;
new = runtime_malloc(cap*sizeof(new[0]));
if(new == nil)
runtime_throw("runtime: cannot allocate memory");
if(runtime_allg != nil) {
runtime_memmove(new, runtime_allg, runtime_allglen*sizeof(new[0]));
runtime_free(runtime_allg);
}
runtime_allg = new;
allgcap = cap;
}
runtime_allg[runtime_allglen++] = gp;
runtime_unlock(&allglock);
}
// Put on gfree list.
// If local list is too long, transfer a batch to the global list.
static void
gfput(P *p, G *gp)
{
gp->schedlink = p->gfree;
p->gfree = gp;
p->gfreecnt++;
if(p->gfreecnt >= 64) {
runtime_lock(&runtime_sched.gflock);
while(p->gfreecnt >= 32) {
p->gfreecnt--;
gp = p->gfree;
p->gfree = gp->schedlink;
gp->schedlink = runtime_sched.gfree;
runtime_sched.gfree = gp;
}
runtime_unlock(&runtime_sched.gflock);
}
}
// Get from gfree list.
// If local list is empty, grab a batch from global list.
static G*
gfget(P *p)
{
G *gp;
retry:
gp = p->gfree;
if(gp == nil && runtime_sched.gfree) {
runtime_lock(&runtime_sched.gflock);
while(p->gfreecnt < 32 && runtime_sched.gfree) {
p->gfreecnt++;
gp = runtime_sched.gfree;
runtime_sched.gfree = gp->schedlink;
gp->schedlink = p->gfree;
p->gfree = gp;
}
runtime_unlock(&runtime_sched.gflock);
goto retry;
}
if(gp) {
p->gfree = gp->schedlink;
p->gfreecnt--;
}
return gp;
}
// Purge all cached G's from gfree list to the global list.
static void
gfpurge(P *p)
{
G *gp;
runtime_lock(&runtime_sched.gflock);
while(p->gfreecnt) {
p->gfreecnt--;
gp = p->gfree;
p->gfree = gp->schedlink;
gp->schedlink = runtime_sched.gfree;
runtime_sched.gfree = gp;
}
runtime_unlock(&runtime_sched.gflock);
}
void
runtime_Breakpoint(void)
{
runtime_breakpoint();
}
void runtime_Gosched (void) __asm__ (GOSYM_PREFIX "runtime.Gosched");
void
runtime_Gosched(void)
{
runtime_gosched();
}
// Implementation of runtime.GOMAXPROCS.
// delete when scheduler is even stronger
int32
runtime_gomaxprocsfunc(int32 n)
{
int32 ret;
if(n > MaxGomaxprocs)
n = MaxGomaxprocs;
runtime_lock(&runtime_sched.lock);
ret = runtime_gomaxprocs;
if(n <= 0 || n == ret) {
runtime_unlock(&runtime_sched.lock);
return ret;
}
runtime_unlock(&runtime_sched.lock);
runtime_semacquire(&runtime_worldsema, false);
m->gcing = 1;
runtime_stoptheworld();
newprocs = n;
m->gcing = 0;
runtime_semrelease(&runtime_worldsema);
runtime_starttheworld();
return ret;
}
// lockOSThread is called by runtime.LockOSThread and runtime.lockOSThread below
// after they modify m->locked. Do not allow preemption during this call,
// or else the m might be different in this function than in the caller.
static void
lockOSThread(void)
{
m->lockedg = g;
g->lockedm = m;
}
void runtime_LockOSThread(void) __asm__ (GOSYM_PREFIX "runtime.LockOSThread");
void
runtime_LockOSThread(void)
{
m->locked |= LockExternal;
lockOSThread();
}
void
runtime_lockOSThread(void)
{
m->locked += LockInternal;
lockOSThread();
}
// unlockOSThread is called by runtime.UnlockOSThread and runtime.unlockOSThread below
// after they update m->locked. Do not allow preemption during this call,
// or else the m might be in different in this function than in the caller.
static void
unlockOSThread(void)
{
if(m->locked != 0)
return;
m->lockedg = nil;
g->lockedm = nil;
}
void runtime_UnlockOSThread(void) __asm__ (GOSYM_PREFIX "runtime.UnlockOSThread");
void
runtime_UnlockOSThread(void)
{
m->locked &= ~LockExternal;
unlockOSThread();
}
void
runtime_unlockOSThread(void)
{
if(m->locked < LockInternal)
runtime_throw("runtime: internal error: misuse of lockOSThread/unlockOSThread");
m->locked -= LockInternal;
unlockOSThread();
}
bool
runtime_lockedOSThread(void)
{
return g->lockedm != nil && m->lockedg != nil;
}
int32
runtime_gcount(void)
{
G *gp;
int32 n, s;
uintptr i;
n = 0;
runtime_lock(&allglock);
// TODO(dvyukov): runtime.NumGoroutine() is O(N).
// We do not want to increment/decrement centralized counter in newproc/goexit,
// just to make runtime.NumGoroutine() faster.
// Compromise solution is to introduce per-P counters of active goroutines.
for(i = 0; i < runtime_allglen; i++) {
gp = runtime_allg[i];
s = gp->status;
if(s == Grunnable || s == Grunning || s == Gsyscall || s == Gwaiting)
n++;
}
runtime_unlock(&allglock);
return n;
}
int32
runtime_mcount(void)
{
return runtime_sched.mcount;
}
static struct {
Lock lock;
void (*fn)(uintptr*, int32);
int32 hz;
uintptr pcbuf[TracebackMaxFrames];
Location locbuf[TracebackMaxFrames];
} prof;
static void System(void) {}
static void GC(void) {}
// Called if we receive a SIGPROF signal.
void
runtime_sigprof()
{
M *mp = m;
int32 n, i;
bool traceback;
if(prof.fn == nil || prof.hz == 0)
return;
if(mp == nil)
return;
// Profiling runs concurrently with GC, so it must not allocate.
mp->mallocing++;
traceback = true;
if(mp->mcache == nil)
traceback = false;
runtime_lock(&prof.lock);
if(prof.fn == nil) {
runtime_unlock(&prof.lock);
mp->mallocing--;
return;
}
n = 0;
if(runtime_atomicload(&runtime_in_callers) > 0) {
// If SIGPROF arrived while already fetching runtime
// callers we can have trouble on older systems
// because the unwind library calls dl_iterate_phdr
// which was not recursive in the past.
traceback = false;
}
if(traceback) {
n = runtime_callers(0, prof.locbuf, nelem(prof.locbuf), false);
for(i = 0; i < n; i++)
prof.pcbuf[i] = prof.locbuf[i].pc;
}
if(!traceback || n <= 0) {
n = 2;
prof.pcbuf[0] = (uintptr)runtime_getcallerpc(&n);
if(mp->gcing || mp->helpgc)
prof.pcbuf[1] = (uintptr)GC;
else
prof.pcbuf[1] = (uintptr)System;
}
prof.fn(prof.pcbuf, n);
runtime_unlock(&prof.lock);
mp->mallocing--;
}
// Arrange to call fn with a traceback hz times a second.
void
runtime_setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
{
// Force sane arguments.
if(hz < 0)
hz = 0;
if(hz == 0)
fn = nil;
if(fn == nil)
hz = 0;
// Disable preemption, otherwise we can be rescheduled to another thread
// that has profiling enabled.
m->locks++;
// Stop profiler on this thread so that it is safe to lock prof.
// if a profiling signal came in while we had prof locked,
// it would deadlock.
runtime_resetcpuprofiler(0);
runtime_lock(&prof.lock);
prof.fn = fn;
prof.hz = hz;
runtime_unlock(&prof.lock);
runtime_lock(&runtime_sched.lock);
runtime_sched.profilehz = hz;
runtime_unlock(&runtime_sched.lock);
if(hz != 0)
runtime_resetcpuprofiler(hz);
m->locks--;
}
// Change number of processors. The world is stopped, sched is locked.
static void
procresize(int32 new)
{
int32 i, old;
bool empty;
G *gp;
P *p;
old = runtime_gomaxprocs;
if(old < 0 || old > MaxGomaxprocs || new <= 0 || new >MaxGomaxprocs)
runtime_throw("procresize: invalid arg");
// initialize new P's
for(i = 0; i < new; i++) {
p = runtime_allp[i];
if(p == nil) {
p = (P*)runtime_mallocgc(sizeof(*p), 0, FlagNoInvokeGC);
p->id = i;
p->status = Pgcstop;
runtime_atomicstorep(&runtime_allp[i], p);
}
if(p->mcache == nil) {
if(old==0 && i==0)
p->mcache = m->mcache; // bootstrap
else
p->mcache = runtime_allocmcache();
}
}
// redistribute runnable G's evenly
// collect all runnable goroutines in global queue preserving FIFO order
// FIFO order is required to ensure fairness even during frequent GCs
// see http://golang.org/issue/7126
empty = false;
while(!empty) {
empty = true;
for(i = 0; i < old; i++) {
p = runtime_allp[i];
if(p->runqhead == p->runqtail)
continue;
empty = false;
// pop from tail of local queue
p->runqtail--;
gp = p->runq[p->runqtail%nelem(p->runq)];
// push onto head of global queue
gp->schedlink = runtime_sched.runqhead;
runtime_sched.runqhead = gp;
if(runtime_sched.runqtail == nil)
runtime_sched.runqtail = gp;
runtime_sched.runqsize++;
}
}
// fill local queues with at most nelem(p->runq)/2 goroutines
// start at 1 because current M already executes some G and will acquire allp[0] below,
// so if we have a spare G we want to put it into allp[1].
for(i = 1; (uint32)i < (uint32)new * nelem(p->runq)/2 && runtime_sched.runqsize > 0; i++) {
gp = runtime_sched.runqhead;
runtime_sched.runqhead = gp->schedlink;
if(runtime_sched.runqhead == nil)
runtime_sched.runqtail = nil;
runtime_sched.runqsize--;
runqput(runtime_allp[i%new], gp);
}
// free unused P's
for(i = new; i < old; i++) {
p = runtime_allp[i];
runtime_freemcache(p->mcache);
p->mcache = nil;
gfpurge(p);
p->status = Pdead;
// can't free P itself because it can be referenced by an M in syscall
}
if(m->p)
m->p->m = nil;
m->p = nil;
m->mcache = nil;
p = runtime_allp[0];
p->m = nil;
p->status = Pidle;
acquirep(p);
for(i = new-1; i > 0; i--) {
p = runtime_allp[i];
p->status = Pidle;
pidleput(p);
}
runtime_atomicstore((uint32*)&runtime_gomaxprocs, new);
}
// Associate p and the current m.
static void
acquirep(P *p)
{
if(m->p || m->mcache)
runtime_throw("acquirep: already in go");
if(p->m || p->status != Pidle) {
runtime_printf("acquirep: p->m=%p(%d) p->status=%d\n", p->m, p->m ? p->m->id : 0, p->status);
runtime_throw("acquirep: invalid p state");
}
m->mcache = p->mcache;
m->p = p;
p->m = m;
p->status = Prunning;
}
// Disassociate p and the current m.
static P*
releasep(void)
{
P *p;
if(m->p == nil || m->mcache == nil)
runtime_throw("releasep: invalid arg");
p = m->p;
if(p->m != m || p->mcache != m->mcache || p->status != Prunning) {
runtime_printf("releasep: m=%p m->p=%p p->m=%p m->mcache=%p p->mcache=%p p->status=%d\n",
m, m->p, p->m, m->mcache, p->mcache, p->status);
runtime_throw("releasep: invalid p state");
}
m->p = nil;
m->mcache = nil;
p->m = nil;
p->status = Pidle;
return p;
}
static void
incidlelocked(int32 v)
{
runtime_lock(&runtime_sched.lock);
runtime_sched.nmidlelocked += v;
if(v > 0)
checkdead();
runtime_unlock(&runtime_sched.lock);
}
// Check for deadlock situation.
// The check is based on number of running M's, if 0 -> deadlock.
static void
checkdead(void)
{
G *gp;
int32 run, grunning, s;
uintptr i;
// For -buildmode=c-shared or -buildmode=c-archive it's OK if
// there are no running goroutines. The calling program is
// assumed to be running.
if(runtime_isarchive) {
return;
}
// -1 for sysmon
run = runtime_sched.mcount - runtime_sched.nmidle - runtime_sched.nmidlelocked - 1 - countextra();
if(run > 0)
return;
// If we are dying because of a signal caught on an already idle thread,
// freezetheworld will cause all running threads to block.
// And runtime will essentially enter into deadlock state,
// except that there is a thread that will call runtime_exit soon.
if(runtime_panicking > 0)
return;
if(run < 0) {
runtime_printf("runtime: checkdead: nmidle=%d nmidlelocked=%d mcount=%d\n",
runtime_sched.nmidle, runtime_sched.nmidlelocked, runtime_sched.mcount);
runtime_throw("checkdead: inconsistent counts");
}
grunning = 0;
runtime_lock(&allglock);
for(i = 0; i < runtime_allglen; i++) {
gp = runtime_allg[i];
if(gp->isbackground)
continue;
s = gp->status;
if(s == Gwaiting)
grunning++;
else if(s == Grunnable || s == Grunning || s == Gsyscall) {
runtime_unlock(&allglock);
runtime_printf("runtime: checkdead: find g %D in status %d\n", gp->goid, s);
runtime_throw("checkdead: runnable g");
}
}
runtime_unlock(&allglock);
if(grunning == 0) // possible if main goroutine calls runtime_Goexit()
runtime_throw("no goroutines (main called runtime.Goexit) - deadlock!");
m->throwing = -1; // do not dump full stacks
runtime_throw("all goroutines are asleep - deadlock!");
}
static void
sysmon(void)
{
uint32 idle, delay;
int64 now, lastpoll, lasttrace;
G *gp;
lasttrace = 0;
idle = 0; // how many cycles in succession we had not wokeup somebody
delay = 0;
for(;;) {
if(idle == 0) // start with 20us sleep...
delay = 20;
else if(idle > 50) // start doubling the sleep after 1ms...
delay *= 2;
if(delay > 10*1000) // up to 10ms
delay = 10*1000;
runtime_usleep(delay);
if(runtime_debug.schedtrace <= 0 &&
(runtime_sched.gcwaiting || runtime_atomicload(&runtime_sched.npidle) == (uint32)runtime_gomaxprocs)) { // TODO: fast atomic
runtime_lock(&runtime_sched.lock);
if(runtime_atomicload(&runtime_sched.gcwaiting) || runtime_atomicload(&runtime_sched.npidle) == (uint32)runtime_gomaxprocs) {
runtime_atomicstore(&runtime_sched.sysmonwait, 1);
runtime_unlock(&runtime_sched.lock);
runtime_notesleep(&runtime_sched.sysmonnote);
runtime_noteclear(&runtime_sched.sysmonnote);
idle = 0;
delay = 20;
} else
runtime_unlock(&runtime_sched.lock);
}
// poll network if not polled for more than 10ms
lastpoll = runtime_atomicload64(&runtime_sched.lastpoll);
now = runtime_nanotime();
if(lastpoll != 0 && lastpoll + 10*1000*1000 < now) {
runtime_cas64(&runtime_sched.lastpoll, lastpoll, now);
gp = runtime_netpoll(false); // non-blocking
if(gp) {
// Need to decrement number of idle locked M's
// (pretending that one more is running) before injectglist.
// Otherwise it can lead to the following situation:
// injectglist grabs all P's but before it starts M's to run the P's,
// another M returns from syscall, finishes running its G,
// observes that there is no work to do and no other running M's
// and reports deadlock.
incidlelocked(-1);
injectglist(gp);
incidlelocked(1);
}
}
// retake P's blocked in syscalls
// and preempt long running G's
if(retake(now))
idle = 0;
else
idle++;
if(runtime_debug.schedtrace > 0 && lasttrace + runtime_debug.schedtrace*1000000ll <= now) {
lasttrace = now;
runtime_schedtrace(runtime_debug.scheddetail);
}
}
}
typedef struct Pdesc Pdesc;
struct Pdesc
{
uint32 schedtick;
int64 schedwhen;
uint32 syscalltick;
int64 syscallwhen;
};
static Pdesc pdesc[MaxGomaxprocs];
static uint32
retake(int64 now)
{
uint32 i, s, n;
int64 t;
P *p;
Pdesc *pd;
n = 0;
for(i = 0; i < (uint32)runtime_gomaxprocs; i++) {
p = runtime_allp[i];
if(p==nil)
continue;
pd = &pdesc[i];
s = p->status;
if(s == Psyscall) {
// Retake P from syscall if it's there for more than 1 sysmon tick (at least 20us).
t = p->syscalltick;
if(pd->syscalltick != t) {
pd->syscalltick = t;
pd->syscallwhen = now;
continue;
}
// On the one hand we don't want to retake Ps if there is no other work to do,
// but on the other hand we want to retake them eventually
// because they can prevent the sysmon thread from deep sleep.
if(p->runqhead == p->runqtail &&
runtime_atomicload(&runtime_sched.nmspinning) + runtime_atomicload(&runtime_sched.npidle) > 0 &&
pd->syscallwhen + 10*1000*1000 > now)
continue;
// Need to decrement number of idle locked M's
// (pretending that one more is running) before the CAS.
// Otherwise the M from which we retake can exit the syscall,
// increment nmidle and report deadlock.
incidlelocked(-1);
if(runtime_cas(&p->status, s, Pidle)) {
n++;
handoffp(p);
}
incidlelocked(1);
} else if(s == Prunning) {
// Preempt G if it's running for more than 10ms.
t = p->schedtick;
if(pd->schedtick != t) {
pd->schedtick = t;
pd->schedwhen = now;
continue;
}
if(pd->schedwhen + 10*1000*1000 > now)
continue;
// preemptone(p);
}
}
return n;
}
// Tell all goroutines that they have been preempted and they should stop.
// This function is purely best-effort. It can fail to inform a goroutine if a
// processor just started running it.
// No locks need to be held.
// Returns true if preemption request was issued to at least one goroutine.
static bool
preemptall(void)
{
return false;
}
void
runtime_schedtrace(bool detailed)
{
static int64 starttime;
int64 now;
int64 id1, id2, id3;
int32 i, t, h;
uintptr gi;
const char *fmt;
M *mp, *lockedm;
G *gp, *lockedg;
P *p;
now = runtime_nanotime();
if(starttime == 0)
starttime = now;
runtime_lock(&runtime_sched.lock);
runtime_printf("SCHED %Dms: gomaxprocs=%d idleprocs=%d threads=%d idlethreads=%d runqueue=%d",
(now-starttime)/1000000, runtime_gomaxprocs, runtime_sched.npidle, runtime_sched.mcount,
runtime_sched.nmidle, runtime_sched.runqsize);
if(detailed) {
runtime_printf(" gcwaiting=%d nmidlelocked=%d nmspinning=%d stopwait=%d sysmonwait=%d\n",
runtime_sched.gcwaiting, runtime_sched.nmidlelocked, runtime_sched.nmspinning,
runtime_sched.stopwait, runtime_sched.sysmonwait);
}
// We must be careful while reading data from P's, M's and G's.
// Even if we hold schedlock, most data can be changed concurrently.
// E.g. (p->m ? p->m->id : -1) can crash if p->m changes from non-nil to nil.
for(i = 0; i < runtime_gomaxprocs; i++) {
p = runtime_allp[i];
if(p == nil)
continue;
mp = p->m;
h = runtime_atomicload(&p->runqhead);
t = runtime_atomicload(&p->runqtail);
if(detailed)
runtime_printf(" P%d: status=%d schedtick=%d syscalltick=%d m=%d runqsize=%d gfreecnt=%d\n",
i, p->status, p->schedtick, p->syscalltick, mp ? mp->id : -1, t-h, p->gfreecnt);
else {
// In non-detailed mode format lengths of per-P run queues as:
// [len1 len2 len3 len4]
fmt = " %d";
if(runtime_gomaxprocs == 1)
fmt = " [%d]\n";
else if(i == 0)
fmt = " [%d";
else if(i == runtime_gomaxprocs-1)
fmt = " %d]\n";
runtime_printf(fmt, t-h);
}
}
if(!detailed) {
runtime_unlock(&runtime_sched.lock);
return;
}
for(mp = runtime_allm; mp; mp = mp->alllink) {
p = mp->p;
gp = mp->curg;
lockedg = mp->lockedg;
id1 = -1;
if(p)
id1 = p->id;
id2 = -1;
if(gp)
id2 = gp->goid;
id3 = -1;
if(lockedg)
id3 = lockedg->goid;
runtime_printf(" M%d: p=%D curg=%D mallocing=%d throwing=%d gcing=%d"
" locks=%d dying=%d helpgc=%d spinning=%d blocked=%d lockedg=%D\n",
mp->id, id1, id2,
mp->mallocing, mp->throwing, mp->gcing, mp->locks, mp->dying, mp->helpgc,
mp->spinning, m->blocked, id3);
}
runtime_lock(&allglock);
for(gi = 0; gi < runtime_allglen; gi++) {
gp = runtime_allg[gi];
mp = gp->m;
lockedm = gp->lockedm;
runtime_printf(" G%D: status=%d(%s) m=%d lockedm=%d\n",
gp->goid, gp->status, gp->waitreason, mp ? mp->id : -1,
lockedm ? lockedm->id : -1);
}
runtime_unlock(&allglock);
runtime_unlock(&runtime_sched.lock);
}
// Put mp on midle list.
// Sched must be locked.
static void
mput(M *mp)
{
mp->schedlink = runtime_sched.midle;
runtime_sched.midle = mp;
runtime_sched.nmidle++;
checkdead();
}
// Try to get an m from midle list.
// Sched must be locked.
static M*
mget(void)
{
M *mp;
if((mp = runtime_sched.midle) != nil){
runtime_sched.midle = mp->schedlink;
runtime_sched.nmidle--;
}
return mp;
}
// Put gp on the global runnable queue.
// Sched must be locked.
static void
globrunqput(G *gp)
{
gp->schedlink = nil;
if(runtime_sched.runqtail)
runtime_sched.runqtail->schedlink = gp;
else
runtime_sched.runqhead = gp;
runtime_sched.runqtail = gp;
runtime_sched.runqsize++;
}
// Put a batch of runnable goroutines on the global runnable queue.
// Sched must be locked.
static void
globrunqputbatch(G *ghead, G *gtail, int32 n)
{
gtail->schedlink = nil;
if(runtime_sched.runqtail)
runtime_sched.runqtail->schedlink = ghead;
else
runtime_sched.runqhead = ghead;
runtime_sched.runqtail = gtail;
runtime_sched.runqsize += n;
}
// Try get a batch of G's from the global runnable queue.
// Sched must be locked.
static G*
globrunqget(P *p, int32 max)
{
G *gp, *gp1;
int32 n;
if(runtime_sched.runqsize == 0)
return nil;
n = runtime_sched.runqsize/runtime_gomaxprocs+1;
if(n > runtime_sched.runqsize)
n = runtime_sched.runqsize;
if(max > 0 && n > max)
n = max;
if((uint32)n > nelem(p->runq)/2)
n = nelem(p->runq)/2;
runtime_sched.runqsize -= n;
if(runtime_sched.runqsize == 0)
runtime_sched.runqtail = nil;
gp = runtime_sched.runqhead;
runtime_sched.runqhead = gp->schedlink;
n--;
while(n--) {
gp1 = runtime_sched.runqhead;
runtime_sched.runqhead = gp1->schedlink;
runqput(p, gp1);
}
return gp;
}
// Put p to on pidle list.
// Sched must be locked.
static void
pidleput(P *p)
{
p->link = runtime_sched.pidle;
runtime_sched.pidle = p;
runtime_xadd(&runtime_sched.npidle, 1); // TODO: fast atomic
}
// Try get a p from pidle list.
// Sched must be locked.
static P*
pidleget(void)
{
P *p;
p = runtime_sched.pidle;
if(p) {
runtime_sched.pidle = p->link;
runtime_xadd(&runtime_sched.npidle, -1); // TODO: fast atomic
}
return p;
}
// Try to put g on local runnable queue.
// If it's full, put onto global queue.
// Executed only by the owner P.
static void
runqput(P *p, G *gp)
{
uint32 h, t;
retry:
h = runtime_atomicload(&p->runqhead); // load-acquire, synchronize with consumers
t = p->runqtail;
if(t - h < nelem(p->runq)) {
p->runq[t%nelem(p->runq)] = gp;
runtime_atomicstore(&p->runqtail, t+1); // store-release, makes the item available for consumption
return;
}
if(runqputslow(p, gp, h, t))
return;
// the queue is not full, now the put above must suceed
goto retry;
}
// Put g and a batch of work from local runnable queue on global queue.
// Executed only by the owner P.
static bool
runqputslow(P *p, G *gp, uint32 h, uint32 t)
{
G *batch[nelem(p->runq)/2+1];
uint32 n, i;
// First, grab a batch from local queue.
n = t-h;
n = n/2;
if(n != nelem(p->runq)/2)
runtime_throw("runqputslow: queue is not full");
for(i=0; i<n; i++)